Confidence Interval Calculator

About This Tool

Look, I get it. You’re staring at a bunch of numbers, trying to figure out what they actually mean. You ran an experiment, collected some data, and now you’re wondering: “How sure am I about this average?” That’s where a confidence interval calculator comes in. It’s not magic, but it’s close. It gives you a range—like a best guess with a little wiggle room—so you can say, “I’m 95% confident the real value falls between X and Y.” No jargon. Just clarity.

I built this because I got tired of digging through stats textbooks every time I needed a quick check. It’s simple, fast, and doesn’t assume you’ve got a PhD in statistics. Whether you’re analyzing survey results, A/B testing a website, or just curious about your data, this tool cuts through the noise.

Key Features

• Calculates confidence intervals for means and proportions—no need to switch tools.
• Supports common confidence levels: 90%, 95%, 99%—because sometimes you need that extra certainty.
• Handles both small and large sample sizes, with automatic checks for normality assumptions.
• Clean, no-nonsense interface. Enter your data, hit calculate, get results. No clutter.
• Explains what the output means in plain English. Because numbers without context are just noise.
• Works offline. No data sent anywhere. Your numbers stay yours.

FAQ

Q: Do I need to know the population standard deviation?
A: Nope. If you don’t have it, the calculator uses your sample standard deviation and adjusts with a t-distribution. It’s smarter than it looks.

Q: What if my sample size is really small?
A: The tool will still work, but it’ll warn you if the sample’s too tiny to trust the results. Better safe than sorry—especially with skewed data.